A polymer electrolyte fuel cell (hereinafter referred to as “PEFC”) generates electric power and heat at the same time through an electrochemical reaction of a fuel gas containing hydrogen and an oxidizing gas containing oxygen etc. in its MEA body part.
Generally, PEFCs are composed of a stack of cells. A cell is formed such that the gaskets on opposed surfaces of the peripheral region of the MEA are sandwiched between a pair of electrically conductive separator plates which are, more particularly, an anode separator plate and a cathode separator plate. The MEA comprises an MEA body part and gaskets provided so as to enclose the MEA body part, being joined to a polymer electrolyte membrane that extends in the peripheral region of the MEA body part, or a combination of a frame and gaskets. The MEA body part is composed of a polymer electrolyte membrane and a pair of electrode layers formed on opposed surfaces of the polymer electrolyte membrane. The surfaces of the electrode layers are exposed to fuel gas and oxidizing gas respectively, thereby causing an electrochemical reaction, while leakage of the fuel gas and oxidizing gas to the outside being shut off or restrained by the gaskets or the frame/gaskets.
One of the serious problems presented by PEFCs is a decline in the fuel gas and oxidizing gas utilization efficiencies. Concretely, there is difficulty in bringing the inner peripheries of the gaskets into perfect contact with the outer peripheries of the electrode layers for the reason such as restraints on the processing steps. That is, a gap (hereinafter referred to as “MEA body part peripheral gap”) is created between the inner periphery of each gasket and the outer periphery of its associated electrode layer. During operation of the PEFC, the fuel gas and oxidizing gas leak into the MEA body part peripheral gaps and are mostly discharged to the outside without being exposed to the MEA body part with the result that the fuel gas and oxidizing gas utilization efficiencies and, in consequence, the efficiency of the polymer electrolyte fuel cell drop. For example, Patent Document 1 has proposed a gasket that is made from a specific rubber material for covering and sealing off the outer periphery of an electrode layer and is integrally formed with the polymer electrolyte membrane.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-155745